test/first_aligned.cpp

// This file is part of Eigen, a lightweight C++ template library
// for linear algebra.
//
// Copyright (C) 2009 Benoit Jacob <jacob.benoit.1@gmail.com>
//
// This Source Code Form is subject to the terms of the Mozilla
// Public License v. 2.0. If a copy of the MPL was not distributed
// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
// SPDX-License-Identifier: MPL-2.0

#include "main.h"

template <typename Scalar>
void test_first_aligned_helper(Scalar *array, int size) {
  const int packet_size = sizeof(Scalar) * internal::packet_traits<Scalar>::size;
  VERIFY(((size_t(array) + sizeof(Scalar) * internal::first_default_aligned(array, size)) % packet_size) == 0);
}

template <typename Scalar>
void test_none_aligned_helper(Scalar *array, int size) {
  EIGEN_UNUSED_VARIABLE(array);
  EIGEN_UNUSED_VARIABLE(size);
  VERIFY(!internal::packet_traits<Scalar>::Vectorizable || internal::first_default_aligned(array, size) == size);
}

struct some_non_vectorizable_type {
  float x;
};

EIGEN_DECLARE_TEST(first_aligned) {
  EIGEN_ALIGN16 float array_float[100];
  test_first_aligned_helper(array_float, 50);
  test_first_aligned_helper(array_float + 1, 50);
  test_first_aligned_helper(array_float + 2, 50);
  test_first_aligned_helper(array_float + 3, 50);
  test_first_aligned_helper(array_float + 4, 50);
  test_first_aligned_helper(array_float + 5, 50);

  EIGEN_ALIGN16 double array_double[100];
  test_first_aligned_helper(array_double, 50);
  test_first_aligned_helper(array_double + 1, 50);
  test_first_aligned_helper(array_double + 2, 50);

  double *array_double_plus_4_bytes = (double *)(std::uintptr_t(array_double) + 4);
  test_none_aligned_helper(array_double_plus_4_bytes, 50);
  test_none_aligned_helper(array_double_plus_4_bytes + 1, 50);

  // alignof(std::complex<double>) == 8 while sizeof(std::complex<double>) == 16; an 8-byte-offset buffer
  // cannot reach >= 16-byte alignment at any element stride.
  EIGEN_ALIGN16 std::complex<double> array_cdouble[100];
  test_first_aligned_helper(array_cdouble, 50);
  test_first_aligned_helper(array_cdouble + 1, 50);
  std::complex<double> *array_cdouble_plus_8_bytes =
      reinterpret_cast<std::complex<double> *>(std::uintptr_t(array_cdouble) + 8);
  test_none_aligned_helper(array_cdouble_plus_8_bytes, 50);
  test_none_aligned_helper(array_cdouble_plus_8_bytes + 1, 50);
  VERIFY_IS_EQUAL(internal::first_aligned<16>(array_cdouble_plus_8_bytes, 50), 50);
  VERIFY_IS_EQUAL(internal::first_aligned<8>(array_cdouble_plus_8_bytes, 50), 0);

  some_non_vectorizable_type array_nonvec[100];
  test_first_aligned_helper(array_nonvec, 100);
  test_none_aligned_helper(array_nonvec, 100);
}